1. Field of the Invention
The present invention relates to methods for the early detection of bladder cancer. In particular, bladder cancer is detected early by use of in situ hybridization of cells obtained from urine or bladder washings.
2. Description of Related Art
The publications and other materials used herein to illuminate the background of the invention and in particular cases to provide additional details respecting its practice are incorporated by reference and for convenience are numerically referenced in the following text and respectively grouped in the appended bibliography.
Cancer of the bladder is the fifth most common cancer in the United States with an annual incidence of about 18 cases per 100,000 or over 50,000 new cases per year, leading to more than 10,000 deaths annually. The incidence (80% of the cases) is highest in the 50-79 year age group; the disease prevalence peaks in the seventh decade of life with a strong male predominance. Bladder cancer accounts for 7% of all new cases of cancer among men and 3% among women, as well as 2% of cancer deaths among men and 1% among women. Occupational exposure may account for 21-25% of bladder cancer in white males in the United States.
Almost all cases of bladder cancer are of the transitional cell type (95%), and among those, approximately 80% appear initially as more or less well-differentiated, superficial papillary neoplasms with a tendency for multifocal or diffuse involvement of the urothelial surface and/or recurrent tumor episodes, but with limited potential for invasive growth.
Of special interest is carcinoma-in-situ (CIS) of the bladder, a lesion presenting problems in diagnosis and of unpredictable behavior (e.g. recurrence and progression) and where morphologic definition is arbitrary and generally defined as a total replacement of the urothelial surface by cells which bear morphologic features of the carcinoma, but which lack architectural alterations other than an increase in the number of cell layers, i.e., a flat lesion.
Cytogenetic analyses of bladder cancer have revealed recurrent abnormalities affecting several chromosomes, particularly structural rearrangements of chromosomes 5 and 9 and numerical changes of chromosome 7, 8, 9 and Y. Rearrangements of chromosomes 1, 10 and 11 have also been reported.
Recently, FISH has become the best alternative method to cytogenetic analysis of bladder cancer. Various studies have described numerical changes of chromosomes 7(+7), 8(+8), 9(xe2x88x929) and Y(xe2x88x92Y) and less frequently 10 and 11.
Bladder cancer affects mostly elderly individuals with a male:female ratio of 5:1 and tends to recur often. Thus, consistent follow-up is imperative for these patients. Follow-up usually consists of cystoscopy, biopsy and x-ray examination. Some of those procedures, though necessary, are considered invasive methods, which are often uncomfortable for the patient. Bladder washings obtained during cystoscopy can be then analyzed histologically and for DNA content. However, that approach is not always successful, particularly when a limited number of cells is present in the sample. In particular, the structural changes i(5q),del(9q) have been often reported and among the numerical changes, xe2x88x92Y, +7, +8 and xe2x88x929 were the most frequently observed. Unfortunately, cytogenetic results on bladder cancer are often difficult to obtain due to the poor growth of tumor cells in culture. In these cases, fluorescense in situ hybridization (FISH) has been used as an alternative technique in detecting numerical chromosome changes. To date, FISH has been performed on cultured cells and paraffin embedded tissue sections of bladder tumors with good results.
Sidransky, et al. [19] analysed tumor cells containing p53 gene mutations shed into the urine.
The present invention is based on the discovery that cells collected from urine or bladder washings may be analyzed by in situ hybridization techniques. One use of this discovery is that such cells may be analyzed to detect bladder cancer or carcinoma in situ. In one aspect, the present invention provides a method for detecting bladder cancer or carcinoma in situ, comprising the steps of:
a) performing in situ hybridization on cells obtained from the urine or bladder washing of a patient by contacting the cells under hybridization conditions with at least one detectable nucleic acid probe which will selectively hybridize to one chromosome in the cells;
b) detecting the hybridized probe; and
c) comparing the results in step b) to a predetermined in situ hybridization pattern obtained from normal cells, wherein the bladder cancer or carcinoma in situ is detected if the results obtained in step b) are different from the predetermined pattern.
The present invention is also directed to kits useful in the practice of the present methods.